Yeah, I don't want ANOTHER splitter off of my only cigar lighter. I've
already got two moving map GPS's plugged into that sucker.
If I install a "power port" in the back seat (under the guidance of my
A&P, of course), do I have to use any kind of a special "aviation power
port" kit -- or can this be any high-quality automotive equivalent that
my A&P will sign off?

Sounds like it's time to add a second battery and alternator with their
own buss. :-))